Pneumatic actuators such as disclosed in U.S. Pat. No. 3,209,537 which provides a rotational output in response to a limited input signal are well known in the art of control mechanisms. The actuator or the present invention is of the continuous rotational category and is to be distinguished from those actuators such as disclosed in U.S. Pat. No. 3,486,518 which provides a rotational output in discrete steps and the continuous rotational actuator which uses a hydraulic servo mechanism to direct the position of the pneumatic supply control valve.
The prior art pneumatic motor actuators are not entirely satisfactory for use in certain operational environments wherein size, weight, reliability and resistance to heat or vibration are of prime concern.